Homeostasis
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Questions and Answers

What typically causes body temperature to fluctuate throughout the day?

  • Variation in activity levels (correct)
  • Dietary changes
  • External weather conditions
  • All of the above

    • Humans lose almost half of their heat energy through conduction.

    False

    What is the normal internal core temperature of the human body?

    37°C

    Heat loss from the body through evaporation occurs via the __________ tract and skin surface.

    <p>respiratory</p> Signup and view all the answers

    Which mechanism of heat transfer involves the movement of warm air away from the skin surface?

    <p>Convection</p> Signup and view all the answers

    Heat input must balance heat output to maintain a stable core temperature.

    <p>True</p> Signup and view all the answers

    Match the following concepts with their descriptions:

    <p>Thermoregulation = Process to maintain core body temperature Acclimatization = Long-term adaptations to changing environmental conditions Heat Production = Internal heat generated during metabolism Heat Loss = Transfer of heat from the body to the external environment</p> Signup and view all the answers

    What range of environmental temperature is considered the thermoneutral zone?

    <p>25–30°C</p> Signup and view all the answers

    What occurs when the core body temperature falls below the thermoneutral zone?

    <p>Heat loss exceeds heat gain</p> Signup and view all the answers

    Central thermoreceptors are located in the skin.

    <p>False</p> Signup and view all the answers

    What is the role of the hypothalamus in thermoregulation?

    <p>It acts as the integrating center for temperature regulation.</p> Signup and view all the answers

    To conserve heat, the body experiences __________ of the cutaneous blood vessels.

    <p>vasoconstriction</p> Signup and view all the answers

    Match the thermoregulatory responses with their purposes:

    <p>Vasoconstriction = To conserve heat Vasodilation = To release heat Sweat glands activation = To cool the body Increased thyroid activity = To boost metabolic rate</p> Signup and view all the answers

    Which of the following is NOT an effector in thermoregulation?

    <p>Kidneys</p> Signup and view all the answers

    Peripheral thermoreceptors monitor core temperature.

    <p>False</p> Signup and view all the answers

    What is the primary purpose of thermoregulatory pathways in mammals?

    <p>To maintain a constant internal body temperature.</p> Signup and view all the answers

    What occurs when the core body temperature increases?

    <p>Increased heat loss</p> Signup and view all the answers

    Vasodilation of skin vessels decreases heat loss from the body.

    <p>False</p> Signup and view all the answers

    What is the main function of the hypothalamus in thermoregulation?

    <p>To maintain temperature homeostasis by activating sympathetic neurons and regulating heat loss.</p> Signup and view all the answers

    Excessive sweating leads to increased heat loss through __________.

    <p>evaporation</p> Signup and view all the answers

    Match each thermoregulatory response with its corresponding effect:

    <p>Vasoconstriction = Decreases heat loss Vasodilation = Increases heat loss Sweating = Enhances surface heat loss Shivering = Produces heat through muscle activity</p> Signup and view all the answers

    During low environmental temperatures, which of the following increases heat production?

    <p>Shivering</p> Signup and view all the answers

    Behavioural responses such as seeking shade help in increasing the body temperature.

    <p>False</p> Signup and view all the answers

    What is the role of vasodilators released by vascular endothelium during thermoregulation?

    <p>They promote blood flow to the skin, enhancing heat loss.</p> Signup and view all the answers

    Study Notes

    Thermoregulation

    • The body maintains a constant internal temperature through homeostatic compensation.
    • Thermoregulatory reflexes help maintain the body's temperature.

    Thermoregulatory Pathways

    • Thermoreceptors are responsible for detecting temperature changes.
      • Central thermoreceptors: Located in the hypothalamus, CNS, and abdominal organs. They monitor core temperature.
      • Peripheral thermoreceptors: Located in the skin. They monitor skin temperature throughout the body.
    • The integrating center for temperature regulation is located in the hypothalamus.
    • Effectors are responsible for responding to temperature changes. These include: skeletal muscles, smooth muscle in arterioles of the skin, sweat glands, adrenal medulla, and thyroid gland.

    Thermoregulatory Responses

    • Alteration in cutaneous blood flow:
      • To conserve heat: Vasoconstriction
        • Blood flow through cutaneous blood vessels is close to zero.
      • To release heat: Vasodilation
        • Nearly 1/3 of cardiac output flows through cutaneous blood vessels.
    • Neural regulation:
      • Most arterioles in the body are under sympathetic control.
        • When core body temperature falls, the hypothalamus activates sympathetic neurons innervating cutaneous arterioles.
        • Vascular smooth muscles contract, causing cutaneous arterioles to constrict, which increases resistance.
        • This diverts blood to lower-resistance blood vessels in the interior of the body.
        • Keeping warmer core blood away from the cooler skin surface reduces heat loss.
        • The opposite happens when core body temperature increases.
      • Local control: Vasodilator released by vascular endothelium.
    • Heat loss by sweating:
      • Evaporation of sweat enhances heat loss through the skin's surface.
      • There are 2-3 million sweat glands.
      • Cooling by evaporation depends on humidity.
    • Heat generation by movement & metabolism:
      • Unregulated heat production:
        • Voluntary muscle contraction.
        • Normal metabolic pathways.
      • Regulated heat production:
        • Maintains temperature homeostasis in low environmental temperatures.
        • Shivering - signals from the hypothalamic thermoregulatory center initiate skeletal muscle tremors. This produces 5-6 times as much heat as resting muscle.
    • Thermogenesis:
      • Low core temperature:
        • Decreases heat loss by vasoconstriction of skin vessels.
        • Behavioral responses such as wearing warm clothing, curling up the body, etc.
        • Increases heat production by increasing muscle tone, shivering, increasing adrenaline secretion, and increasing food appetite.
      • High core temperature:
        • Increases heat loss by vasodilation of skin vessels and sweating.
        • Behavioral responses such as wearing cooler clothing, seeking shade, etc.
        • Decreases heat production by decreasing muscle tone, voluntary activity, decreasing adrenaline secretion, and decreasing food appetite.

    Body Temperature

    • Internal core temperature is approximately 37°C.
    • Normal variations of body temperature exist:
      • Different body regions: rectal temperature is about 0.5°C higher than oral temperature.
      • Different activity patterns and changes in external temperature.
      • Circadian fluctuation of ~1°C during a day.
      • Fluctuation in women at different stages of the menstrual cycle.

    Heat Loss & Heat Gain

    • Heat input must balance heat output to maintain a stable core temperature.
      • Heat input (heat gain):
        • Heat gain from the external environment.
        • Internal heat production.
      • Heat output (heat loss):
        • Heat loss from exposed body surfaces to the external environment.
    • When core temperature decreases, heat loss decreases, and heat production increases.
    • When core temperature increases, heat loss increases, and heat production decreases.

    Mechanisms of Heat Transfer

    • Four primary mechanisms of heat transfer:
      • Radiation:
        • Emission of heat energy from a surface in the form of electromagnetic waves (infrared).
        • Net heat transfer always goes from warmer objects to cooler objects.
        • Humans lose almost half of their heat energy through radiation.
      • Conduction:
        • Transfer of heat between objects of differing temperatures that are in direct contact.
        • Heat moves from the warmer object to the cooler object.
      • Convection:
        • Transfer of heat energy by air (or water) currents, like the heat loss felt on a windy day.
        • Warm air moves away from the skin surface.
        • Clothing traps air and prevents convective air currents, retaining heat close to the body.
      • Evaporation:
        • Heat loss from the body through water evaporation from the skin surface or respiratory tract.

    Thermoneutral Zone

    • This is the environmental temperature range (25–30°C) in which heat generated by normal metabolism is sufficient to maintain body temperature.
    • Above the thermoneutral zone: Heat gain is greater than heat loss.
    • Below the thermoneutral zone: Heat loss is greater than heat gain.

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    Related Documents

    MED1001 Human Physiology Lecture 01 – Homeostasis PDF

    Description

    This quiz explores the mechanisms of thermoregulation within the human body. It covers the roles of thermoreceptors, the hypothalamus as the integrating center, and various physiological responses that help maintain internal temperature. Test your understanding of how the body regulates heat through reflexes and blood flow alterations.

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